Automotive steering columns typically include a mast jacket rigidly attached to the vehicle body, a steering shaft rotatably supported in the mast jacket, and a steering wheel on the upper end of the steering shaft. For absorbing energy, the mast jacket usually includes a lower section anchored to the body and an upper section releasably attached to the body such that compressive force on the steering wheel releases the upper section and initiates telescopic collapse thereof over the lower section. An energy absorbing medium, such as a roll deformer in an overlap between the upper and lower mast jacket sections, resists telescopic collapse at a predetermined rate. The steering shaft is not usually an energy absorbing unit of the steering column and, therefore, typically includes upper and lower elements interconnected by a coupling which joins the elements for unitary rotation without significantly restraining the shaft elements in the direction of the longitudinal centerline of the steering column. Commonly, such steering shaft couplings include a non-circular bar end on one shaft element received and slidable in a correspondingly non-circular tube end on the other shaft element. A shaft assembly according to this invention includes a coupling between upper and lower shaft elements exhibiting reduced friction during longitudinal collapse in comparison with the aforesaid sliding couplings and, therefore, is particularly suited for application as a steering shaft in an energy absorbing steering column.